Polposipus herculeanus 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Arthropoda Insecta Coleoptera Tenebrionidae

Scientific Name: Polposipus herculeanus
Species Authority: Solier, 1848
Common Name(s):
English Frigate Island Giant Tenebrionid Beetle, Fregate Island Giant Tenebrionid Beetle
Pulposipes herculenaus Solier

Assessment Information [top]

Red List Category & Criteria: Vulnerable D2 ver 3.1
Year Published: 2014
Date Assessed: 2013-11-16
Assessor(s): Gerlach, J.
Reviewer(s): Pearce-Kelly, P.
This species was formerly categorised as Critically Endangered due to the threat from introduced rats. These were subsequently eradicated and no currently active threats have been identified. However, with its extremely restricted range the species is vulnerable to future invasions of predators or to natural disasters. Climate change is likely to lead to habitat alteration in the future, with unknown impacts on the beetle.
Previously published Red List assessments:
1996 Critically Endangered (CR)
1994 Rare (R)
1990 Rare (R)
1988 Rare (R)
1986 Rare (R)
1983 Rare (R)

Geographic Range [top]

Range Description: This species is restricted to the Seychelles island of Fregate. In 1861 one specimen was collected on Round Island, Mauritius. It has not been located there since.
Countries occurrence:
Regionally extinct:
Estimated area of occupancy (AOO) - km2: 2
Continuing decline in area of occupancy (AOO): No
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 2
Continuing decline in extent of occurrence (EOO): No
Extreme fluctuations in extent of occurrence (EOO): No
Number of Locations: 1
Continuing decline in number of locations: No
Extreme fluctuations in the number of locations: No
Lower elevation limit (metres): 2
Upper elevation limit (metres): 200
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Censuses of the population on Fregate island were carried out in 1999, 2002 and 2011. The most recent estimate was 54,351 adults (range 43,511-67,879), an increase of 4,000 over the previous census, but 2,700 fewer than in 1999. There is considerable overlap of these estimates and they are only suggestive of recent increases.
Current Population Trend: Stable
Additional data:
Number of mature individuals: 54350 Continuing decline of mature individuals: No
Extreme fluctuations: No Population severely fragmented: No

Habitat and Ecology [top]

Habitat and Ecology: These are large flightless beetles found in coastal woodland where adults are arboreal during the day. They graze on fungi, algae and lichen on tree trunks or descend to the ground at night to forage on leaves, fruit and fungi. Eggs are laid in rotten logs and the larvae feed on the decomposing wood. Eggs take two weeks to hatch, there are seven larval instars and pupation takes 34 days. Development takes 6-8.5 months from egg laying to emergence of adults and adults are sexually mature from within 4-6 weeks of emergence. Generation time has been calculated as 7-10 months.
Systems: Terrestrial
Continuing decline in area, extent and/or quality of habitat: No
Generation Length (years): 0.58-0.83
Movement patterns: Not a Migrant

Threats [top]

Major Threat(s): The species has been threatened by habitat loss in the past but is currently recovering. Its extinction on Round Island, Mauritius can be attributed to habitat destruction caused by introduced rabbits and goats. Fregate island was largely cleared and planted with introduced trees in the 1800s and the beetles were scarce until the mid 1900s. It has adapted to some introduced trees but is now benefiting from habitat restoration. From the 1970s it was reported to be associated with the introduced tree Pterocarpus indicus, this declined after 2000 due to a fungal pathogen but habitat restoration ensured that the beetle population did not decline. Brown rats Rattus norvegicus invaded Fregate island in the 1990s and catastrophic loss was feared. There were some reports of decline from monitoring studies but these were not supported statistically. The rats were subsequently eradicated and beetle populations appear to have remained stable through the phases of rat invasion and eradication. Climate change is causing significant changes in weather patterns in Seychelles (increasing temperatures and rainfall changes) and these are likely to cause changes to habitats, which may affect populations of the beetle in the future.

Conservation Actions [top]

Conservation Actions: Fregate island is a privately owned island subject to tourism and conservation management. The beetle depends upon the woodland habitat which has been improving in recent years due to a forest restoration programme. A recent change in ownership may result in management changes in the future. Climate change is likely to result in changes in forest composition which will have as yet unknown impacts on the beetle, combined with a restricted range and lack of dispersal abilities, this makes the species Vulnerable.

Citation: Gerlach, J. 2014. Polposipus herculeanus. The IUCN Red List of Threatened Species 2014: e.T17902A21425713. . Downloaded on 25 November 2015.
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